In a myoelectrically controlled prosthetic device, a motor controls the device in response to electrical signals from a muscle when the muscle contracts. The signals are received from an electrode or an electrode pair which is positioned on the skin surface adjacent the muscle. Myoelectric control is common in prosthetic arms, but can be used for other prosthetic devices.
To fit a patient with a myoelectric prosthetic device, a prosthetist or therapist tests the patient to determine the best place on the muscle to position the myoelectrode which may be an electrode pair. Generally, the optimal position is one where the myoelectric signal is strong in response to a contraction. For people with an intact muscle, the locations for a strong response are predictable. But for patients who are missing a portion of a limb, whether due to accident or birth defect, it is not uncommon that the remaining muscle remnant will not be otherwise intact and will not respond in the same manner as a muscle on a person with an intact limb.
Typically, a prosthetist uses a trial and error approach to determine the optimal position of an electrode pair. The prosthetist moves a single electronic probe over different portions of the muscle and requests that the patient contract the muscle each time the probe is positioned at a new location. As the prosthetist moves the electrodes to different locations in this manner, the prosthetist tries to locate the position in which the strongest signals are received. The resulting signals from separate contractions are inconsistent, however, because the effort expended by the patient is itself inconsistent from one contraction to another. Moreover, a patient may fatigue quickly when using a muscle that has remained dormant for several months. Consequently, the comparisons between locations are not based on identical conditions.
It would be desirable for a prosthetist to be able to simultaneously test locations on the muscle at the same time over a range of locations, and to compare the responses.
The patient should be trained to use the prosthetic device. For an amputee, the muscle contractions utilized to perform different tasks are not necessarily the same, natural contractions that the patient would have been using to perform those tasks prior to amputation. Accordingly, it would be desirable to have a system for assisting in training patients with new prosthetic devices.